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Recommendations Summary

CF: Fiber Intake 2020

Click here to see the explanation of recommendation ratings (Strong, Fair, Weak, Consensus, Insufficient Evidence) and labels (Imperative or Conditional). To see more detail on the evidence from which the following recommendations were drawn, use the hyperlinks in the Supporting Evidence Section below.


  • Recommendation(s)

    CF: Fiber Intake

    For individuals with cystic fibrosis (CF), the RDN or international equivalent may suggest dietary fiber intake in line with the Dietary Reference (DRI) Intake for the general population, as tolerated on an individual basis, since evidence suggests fiber intake at the recommended level does not increase risk of constipation, diarrha/steatorrhea (DIOS), or other gastrointestinal symptoms.

    Rating: Weak
    Conditional

    • Risks/Harms of Implementing This Recommendation

      Fiber intake that is too high may exacerbate gastrointestinal symptoms in some individuals with cystic fibrosis. Fiber intake that is too low may increase risk of constipation.

    • Conditions of Application

      Individualized MNT. Dietary fiber recommendations should be adjusted according to gastrointestinal symptoms and individual tolerance. Nutrition counseling regarding fiber intake should consider past responses to fiber, dietary preferences, and meal patterns. Spreading fiber intake throughout the day may alleviate gastrointestinal symptoms associated with elevated fiber intake.

    • Potential Costs Associated with Application

      There are no obvious costs associated with this recommendation. Foods with dietary fiber are generally easily accessible, but socioeconomic and environmental factors should be considered when advising individuals with cystic fibrosis how to improve their fiber intake.

    • Recommendation Narrative

      Background. Cystic fibrosis (CF) can have a significant impact on gastrointestinal function for affected individuals due to pancreatic insufficiency and intestinal malabsorption. For individuals with CF, the optimal fiber intake is unclear. In the general population, adequate fiber intake is associated with normalized bowel movements and improved bowel health, as well as improved glucose and lipid values (Linus Pauling Institute, 2019). However, malabsorption and gastrointestinal symptoms are common in individuals with CF, and a diet too high or low in fiber may exacerbate these conditions. 

      Evidence. Limited, observational evidence suggests that fiber intake up to the recommended intake for the general population does not exacerbate GI symptoms, including constipation and DIOS in pediatric participants (Declercq et al 2015, Proesmans and De Boeck 2002, van der Doef et al, 2010). In one study with pediatric participants, the group with DIOS had actual fiber intake greater than the recommended intake, while those with no gastrointestinal symptoms consumed fiber intake at the recommended level (Proesmans and De Boeck 2002).

    • Recommendation Strength Rationale

      The recommendation for fiber intake was rated as Weak/Limited since there were no trials investigating the effect of fiber intake on outcomes of interest. Three observational studies examined the relationship between fiber intake and constipation, gastrointestinal symptoms and DIOS, but two of these studies demonstrated risk of bias and sample sizes were small, resulting in Grade III evidence.

    • Minority Opinions

      Consensus reached.